Non-woven structures are known for use as conveyor belts, for example, as dryer felts or fabrics in papermaking applications. In particular, non-woven fabrics made from a plurality of intermeshed spiral coils that extend in side-by-side relationship in the cross-machine direction and in which adjacent coils are joined together by cross-machine direction hinge members, are useful for papermaker's dryer fabrics. In some cases the spiral fabric is excessively permeable to air and moisture. The permeability may be reduced by inserting a stuffer through the coils between the hinge members of the fabric.
An advantage of spiral link fabric belts is that the smooth, open, monofilament structure greatly reduces the amount of process contaminants held by the belt and enables the belt to withstand flattening, imparting a constant permeability to the belt:. This is necessary for drying paper evenly (British Patent No. GB-B-2,051,154). However, the high permeability of 500-1000 cfm creates a boundary layer of air within and on the surface of the belt, thereby disturbing the conveying of a sheet from one drying cylinder to another due to air being pumped through the permeable fabric. To reduce the permeability, stuffer materials are introduced into the spirals, such as tape, monofilament or flat yarn (British Patent No. GB-B-2,083,431), filler strands which are then subjected to heat treatment to create expansion of the coil (U.S. Pat. No. 4,381,612), open cell elastomeric foam material (British Patent No. GB-B-2,148,337), elastomeric strips introduced into the coils under tension and then released to effect an expansion of the coil (German patent DE 3,907,561) and tapes having a regular array of holes (U.S. Pat. No. 4,839,213). Permeabilities of 150-500 cfm can be achieved using such modified spiral fabrics. However, flat multi-/monofilaments tend to work out of the fabric if the edge sealant becomes damaged, and multifilament stuffer yarns have a tendency to hold more process contaminants than is acceptable. Additionally multifilaments are prone to damage if high pressure cleaning systems are employed.